p.serif,h1.serif {font-family: Times, "Times New Roman", serif}
p.sanserif {font-family: Segoe UI, Helvetica, Arial, sans-serif}
p.monspace {font-family: "Bitstream Vera Sans Mono", Monaco, "Courier New", Courier, monospace}
p.normal {font-style: normal}
p.italic {font-style: italic}
p.oblique {font-style: oblique}
    /*但区别在于Italic是指斜体字，而Oblique是倾斜的文字
    对于没有斜体的字体应该使用Oblique属性值来实现倾斜的文字效果*/
p {font-size: 20px}
p.lighter {font-weight: lighter}
p.thick {font-weight: bold}
p.thicker {font-weight: 1000}
p.font_all {font: 20px lighter monospace}
